L/D study via low-flux neutron imaging with TRAPY

Abstract

The teaching and research reactor AKR-2 of the Technische Universität Dresden (TUD) is a neutron source with a very low neutron flux and provides very difficult radiation field conditions for neutron radiography. On the one hand the radiation field contains both neutrons and gamma particles, on the other hand the neutron field covers the complete energy spectrum of the reactor, i.e. from the thermal Maxwell spectrum to the (fast) fission spectrum. In this context, neutron imaging with thermal neutrons was carried out at the AKR-2 with the aim of demonstrating the feasibility of this method in the sense of a proof of concept at a very low-flux neutron source with difficult neutron field conditions. This investigation is a follow-up to a previous study using a low-budged imaging system called DELCam that showed promising results and therefore motivated to continue this investigation with a state-of-the-art imaging setup called TRAPY. In the framework of this investigation, an L/D study with a tilted cadmium double-edge has been conducted to characterize the new imaging setup and to determine a useful relation between an acceptable L/D and exposure time for imaging at AKR-2.Furthermore, due to the difficult radiation field conditions at the AKR-2, a more robust estimator and a pragmatic deviation measure are needed. In this context, the median and the median absolute deviation (MAD) seem to be appropriate. Finally, neutron imaging at the AKR-2 (as a representative of a very low neutron flux facility) is a useful tool not only to introduce this non-destructive method to the next generation of scientists and engineers, but also for research where low spatial resolution and long exposure time is acceptable. This makes very low neutron flux facilities, such as the AKR-2, interesting for preparatory measurements for high-flux imaging and thus contributes to increasing the availability of the neutron imaging method in research.